This IS a good documentary, about an elementary figure in the history of cinema. Any student of the motion picture, or of American culture, would do well to view it.
However, the main reason I'm posting is to comment on an observation by one of the reviewers here regarding the reputation of Abraham Lincoln in the American South. In THE BIRTH OF A NATION (1915) and in his later ABRAHAM LINCOLN (1930), Griffith echoed the prevailing view among white Southerners in 1865 (the year the Civil War ended) that Lincoln would exact no vengeance on the former Confederacy and would administer a gentle peace. Lincoln's assassination was viewed by many Southerners, certainly in hindsight, as a tragedy for the South, because Lincoln's successor lacked the political clout and popular support to hold vindictive "Radical Republicans" in check. Had Lincoln lived, many Southerners believed, the years of Reconstruction would have been a lot more productive (for whites, at least). Lincoln was certainly no "hero" to most white Southerners during the Civil War itself -- his election in November 1860 was the event that sparked secession and the Civil War -- but after 1865, white Southerners adopted the "martyred" Lincoln as the Hero Who Would Have Saved the White South, and that's the way Griffith portrayed him in his films.